I can't figure out my intermittent 4wd problem. 99% of the time my 4hi doesn't engage and when it does it will eventually disengage on its own. 4lo engages and stays engaged just fine and would think this would eliminate a broken fork at the differential. Dealer put my truck on their diagnostic machine and it didn't throw any codes. Switching to 4hi or 4lo - indicator lights work, transfer case locks, actuator at differential moves, but I dont have 4hi. If I drive around enough, maybe it will kick in, but will also eventually disengage. Switching back to 2wd from 4hi or 4lo - everything goes back the way they should.

Forgot to add that this is an electronic system with the three-position switch next to the climate control fan switch.

 

you get your 4wd high and low from your transfer case sound to me that your motor on your transfer case is not engaging it all the way or may have a short in the wires or motor just going bad you dont have lock in lock out hubs do you or any grinding sounds from the front end when it jumps into 4wd high

 

i agree with labc26. your front axle is engaging if you are getting 4 LO good. THE HI- LO part of the system is controlled by the electric motor on the side of the transmissioni transfer case. could be motor, or could be internal jumping out of gear--- but i would look at the motor stroke toward the HI position.

 

Thanks for the info. I'll check out the motor. I would have thought the dealership would've caught that when they put it on the diagnostic machine.

 

I have a similar problem, except I don’t think my 4H engages at all. Was looking for answers on YouTube, no luck. Hope to get it fixed before winter 🤞

 

Well, this is an unusual situation.
Reason: The front axle lockup is the same for both 4h and 4l, so nothing changes between them. The front has to lock up in 4H first.
Working backwards, the transfer case motor runs to it's first position to engage the case drive train with the transmission. If you have 4L this has worked or 4L could not power the wheels.
In 4 L, the case motor runs to it's second position. This changes [to gear reduction] for 4L and changes the shift RPM the computer does for that low gearing. That works according you.
Explain how you positively know 4H does not function..
The only possibility is the dash switch circuit may be faulty. When the switch is rotated to the 4H position, it is a request to the GEM module to run the transfer case motor to it's first position, engage the transmission with the transfer case and lock up the front axle.
If these circuits work for 4L they have to work for 4H first.
When returning back to 2WD, the front unlocks, the case motor runs backward by a relay that reverses DC voltage to the case motor causing it to run in reverse. If you get back to 2WD this also works unless there is an intermittent of some sort. An intermittent is hard to pin down except from the symptoms and what does or does not work in the chain of events.
There is not much more to it.
Be sure what you have..

 

I was stuck in my yard, turned on 4H, back wheels were spinning, front were not. Put in 4L and got unstuck. I have tried 4H several times since, with no indication of it working, but being in 4L seems to get me where I want to go. 🤔 What you are saying is what I had assumed, but now I’m totally lost.

 

If 4H does not move the front wheels, the front is not locked up.
Find out why.
The only difference is the position of the Transfer case motor.
Look at the Circuit Board contact areas for the first motor position and compare to the area of the second position.
The first position as does the second position operates the firewall solenoid to transfer engine Vacuum to the Actuator and keeps it operated as long a 4wd is requested by the Switch via the GEM and case motor position.
Also notice the dash lights, if none come on in the right sequence, the case motor has not returned the operate signal back to the GEM that lights the dash lamps..
Good luck.

 

What circuit board? In the switch, or on the motor? My dash lights show 4H & 4L according to switch position.

 

The dash switch does not turn on the dash lights directly..
The >>wiper<< contacts on the rear of the case motor circuit board pass the Lamp signal as the firewall solenoid operates, therefore is position sensitive.
You have to take the motor off to check them.
Again, if the front wheels do not turn, even one, the front is not locked up or the drive shaft is not being powered from the transfer case..
The front carrier is the equivalent to an open differential and depends on traction from both wheels, or only one will spin under power. It has no traction Lok like a Rear. The Right CV axle is locked up making it the same as an open rear that would spin one wheel if the other side has no traction because there are differential gears the same as the Rear..
If there was Traction Lok present, it would be a night mare to steer in 2wd. around a corner 'without' 4wd even being engaged..

 

I noticed that when I shift to 4L, it automatically turns traction control off, should I turn it off manually for 4H? Do you think replacing the shift motor will fix the problem, or do you think it’s much worse than that?

 

What are we missing here? There is no separate traction control function on an 2003 model year!
Are you playing a joke with this thread?
I am beginning not to trust what you reply with.
If you have an issue, time to get your hands dirty working on the problem and stop the questions.
You have enough information now to find the cause.
Good luck..

 

I’m sorry, you must have missed where I listed my truck, mine is the 2011 F-250 Powerstroke. The originator off the thread has the 03 F-150.

 

Now you see why it's not appropriate to jam in on another thread you had not started.
To many do this and results in this confusion.
I do not go back investigating what other trucks are involved or who has what year.
You should have stated what truck you have to be sure this does not happen. Simply cannot assume all is known.
Your 4wd is completely different than an 03.
That's why the tip off was the questions being asked.
Yes I got misled but, to a limit that brought about this.
Thank you for clearing the air.
Good luck.

 

Hopefully someone can help.